The present invention relates to the technical field of combustion chambers for turbine engines. It is aimed in particular at a thermal protection shield, or deflector, for a combustion chamber endwall. It is also aimed at a combustion chamber provided with at least one such deflector. It is finally aimed at a turbine engine equipped with such a combustion chamber and/or with at least one such deflector.
Throughout the following, the terms “axial”, “radial” and “transverse” correspond to an axial direction, a radial direction and a transverse plane of the turbine engine respectively, and the terms “upstream” and “downstream” correspond to the gas flow direction in the turbine engine respectively.
A conventional “divergent” combustion chamber is illustrated in FIG. 11, which is an axial section showing one half of the combustion chamber, the other half thereof being derived by symmetry with respect to the axis (not shown) of the turbine engine. The combustion chamber 110 is contained within a diffusion chamber 130 which is an annual space defined between an external casing 132 and an internal casing 134, into which space is introduced a compressed oxidant originating upstream from a compressor (not shown) by way of an annular diffusion duct 136.
This conventional “divergent” combustion chamber 110 comprises an external wall 112 and an internal wall 114 which are coaxial and substantially conical and which widen out from upstream to downstream with a cone angle α. The external 112 and internal 114 walls of the combustion chamber 110 are connected to one another toward the upstream end of the combustion chamber by a chamber endwall 116.
The chamber endwall 116 is a substantially frustoconical component which extends between two substantially transverse planes while widening out from downstream to upstream. The chamber endwall 116 is connected to each of the two external 112 and internal 114 walls of the combustion chamber 110. Owing to the small inclination of the combustion chamber 110, the chamber endwall 116 has a small conical taper. It is provided with injection systems 118 through which there pass injectors 120 which introduce fuel at the upstream end of the combustion chamber 110 where the combustion reactions take place.
These combustion reactions have the effect of radiating heat from downstream to upstream in the direction of the chamber endwall 116. To prevent this chamber endwall 116 from being damaged due to the heat, thermal protection shields, also termed deflectors 122, are provided. These deflectors 122 are substantially flat plates which are arranged on and fastened by brazing to an inner face of the chamber endwall 116. They are cooled by means of cooling air jets which enter the combustion chamber 110 through cooling orifices 124 drilled in the chamber endwall 116. These air jets, which flow from upstream to downstream, are guided by chamber fairings 126, cross the chamber end wall 116 through the cooling orifices 124, and impact on an upstream face of the deflectors 122.
In more recent designs of “convergent” combustion chambers, the external and internal walls of the combustion chamber are inclined by widening out from downstream to upstream, and not from upstream to downstream as in the case of the conventional “divergent” combustion chambers described above. These “convergent” combustion chambers can have a larger cone angle α than the cone angle α of the “divergent” combustion chambers.
Such a large inclination of the combustion chamber has repercussions on the conical taper of the chamber endwall and on the position of the deflectors with respect to the chamber endwall. Such a combustion chamber is partially illustrated in FIG. 12, in axial section. This figure shows an axial direction 100 parallel to the axis of the turbine engine, the main direction 200 of the combustion chamber 110, and the angle α between these two axes 100, 200. Owing to the large inclination of the combustion chamber 110, the chamber endwall 116 has a larger conical taper than a traditional combustion chamber endwall. When not only the inclination of the chamber endwall 116 is large but also the injectors 120 are present in a small number and/or the combustion chamber 110 has a small diameter, that affects the distance D between the chamber endwall and the planar deflectors. In the plane of the axial section shown in FIG. 12, the distance D between the chamber endwall 116 and the deflectors 122 appears to be constant. However, as illustrated in FIG. 13, which is a section on the plane XIII-XIII in FIG. 12, this distance D diminishes as it extends over a circumferential generatrix of the chamber endwall 116, to a point such that the chamber endwall 116 and the deflectors 122 can come into contact. Such a contact between these components is detrimental to a correct assembly of the deflectors in the combustion chamber. The fact that the distance D between the chamber endwall 116 and the deflector 122 is not constant is detrimental to good cooling of said deflector 122.